This invention relates generally to encapsulation structures and methods of organic electroluminescence devices. More particularly, this invention relates to the encapsulation structures and methods of the organic electroluminescence devices being resistant to moisture and/or oxygen.
Organic light emitting devices (OLEDs) generally comprise multiple thin film layers formed on a substrate such as glass or silicon. A light-emitting layer of a luminescent organic solid, as well as optional adjacent semiconductor layers, is sandwiched between a cathode and an anode. The semiconductor layers may be hole-injecting or electron-injecting layers. The light-emitting layer may be selected from any of a multitude of fluorescent or phosphorescent organic solids and may comprise multiple sublayers or a single blended layer.
When a potential difference is applied across the anode and cathode, electrons move from the cathode to the optional electron-injecting layer and finally into the layer(s) of organic material. At the same time, holes move from the anode to the optional hole-injecting layer and finally into the same organic light-emitting layer(s). When the holes and electrons meet in the layer(s) of organic material, they combine and produce photons. The wavelength of the photons depends on the material properties of the organic material in which the photons are generated, and the color of light emitted from the OLED can be controlled by the selection of the organic material, or by the selection of dopants, or by other techniques known in the art.
In a typical OLED, either the anode or the cathode is transparent in order to allow the emitted light to pass through. If it is desirable to allow light to be emitted from both sides of the OLED, both the anode and cathode can be transparent.
The OLEDs have a number of beneficial characteristics, such as a low activation voltage, quick response, high brightness, high visibility, and uncomplicated process of fabrication. Thus, the OLEDs represent a promising technology for display applications and for general illumination.
However, although substantial progresses have been made in the development of the OLEDs to date, additional challenges still remain. For example, the OLEDs continue to face challenges associated with their long-term stability. One of the challenges limiting the widespread use of the OLEDs has been the fact that the organic polymers or small molecule materials making up the device as well as, in some cases, the electrodes, are environmentally sensitive. In particular, it is well known that device performance degrades in the presence of moisture and/or oxygen.
Therefore, there is a need for a new and improved encapsulation structure and method of the OLEDs.